U.S. patent number 10,468,244 [Application Number 15/681,102] was granted by the patent office on 2019-11-05 for precursors and flowable cvd methods for making low-k films to fill surface features.
This patent grant is currently assigned to VERSUM MATERIALS US, LLC. The grantee listed for this patent is Versum Materials US, LLC. Invention is credited to Xinjian Lei, Jianheng Li, Robert Gordon Ridgeway, Raymond Nicholas Vrtis, Manchao Xiao.
United States Patent |
10,468,244 |
Li , et al. |
November 5, 2019 |
Precursors and flowable CVD methods for making low-K films to fill
surface features
Abstract
A method for depositing a silicon-containing film, the method
comprising: placing a substrate comprising at least one surface
feature into a flowable CVD reactor which is at a temperature of
from about -20.degree. C. to about 400.degree. C.; introducing into
the reactor at least one silicon-containing compound having at
least one acetoxy group to at least partially react the at least
one silicon-containing compound to form a flowable liquid oligomer
wherein the flowable liquid oligomer forms a silicon oxide coating
on the substrate and at least partially fills at least a portion of
the at least one surface feature. Once cured, the silicon oxide
coating has a low k and excellent mechanical properties.
Inventors: |
Li; Jianheng (Santa Clara,
CA), Vrtis; Raymond Nicholas (Orefield, PA), Ridgeway;
Robert Gordon (Quakertown, PA), Xiao; Manchao (San
Diego, CA), Lei; Xinjian (Vista, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Versum Materials US, LLC |
Allentown |
PA |
US |
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Assignee: |
VERSUM MATERIALS US, LLC
(Tempe, AZ)
|
Family
ID: |
61243296 |
Appl.
No.: |
15/681,102 |
Filed: |
August 18, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20180061636 A1 |
Mar 1, 2018 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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62381222 |
Aug 30, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07F
7/1896 (20130101); H01L 21/02214 (20130101); C23C
16/50 (20130101); C23C 16/401 (20130101); H01L
21/02203 (20130101); C01B 33/126 (20130101); C23C
16/045 (20130101); C23C 16/56 (20130101); H01L
21/02274 (20130101); H01L 21/02348 (20130101); H01L
21/02211 (20130101); H01L 21/02126 (20130101); H01L
21/02216 (20130101); C09D 7/61 (20180101); C09D
1/00 (20130101) |
Current International
Class: |
H01L
21/02 (20060101); C07F 7/18 (20060101); C23C
16/40 (20060101); C23C 16/56 (20060101); C09D
7/61 (20180101); C09D 1/00 (20060101); C23C
16/50 (20060101); C01B 33/12 (20060101); C23C
16/04 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Peng; Kuo Liang
Attorney, Agent or Firm: Boyer; Michael K. Benson; David
K.
Parent Case Text
This Application claims the benefit of Application No. 62/381,222,
filed on Aug. 30, 2016. The disclosure of Application No.
62/381,222 is hereby incorporated by reference.
Claims
The invention claimed is:
1. A method for depositing a silicon-containing film, the method
comprising: placing a substrate comprising at least one surface
feature into a reactor which is at a temperature of from about
-20.degree. C. to about 400.degree. C.; introducing into the
reactor at least one silicon-containing compound having at least
one acyloxy group, wherein the at least one silicon-containing
compound is an acyloxysilane having a structure: ##STR00004##
wherein R is selected from the group consisting of hydrogen, and a
linear or branched C.sub.1 to C.sub.6 alkyl group; R.sup.1 is
selected from the group consisting of a linear or branched C.sub.1
to C.sub.6 alkyl group, a linear or branched C.sub.2 to C.sub.6
alkenyl group, and a linear or branched C.sub.2 to C.sub.6 alkynyl
group; and providing an in-situ plasma or remote plasma source to
the reactor to at least partially react the at least one
silicon-containing compound to form a flowable liquid oligomer
wherein the flowable liquid oligomer forms a coating on the
substrate and at least partially fills at least a portion of the at
least one surface feature.
2. The method of claim 1 wherein the plasma is selected from the
group consisting of an in-situ or remote plasma source based plasma
comprising nitrogen, an in-situ or remote plasma source based
plasma comprising nitrogen and helium, an in-situ or remote plasma
source based plasma comprising nitrogen and argon, an in-situ or
remote plasma source based plasma comprising ammonia, an in-situ or
remote plasma source based plasma comprising ammonia and helium, an
in-situ or remote plasma source based plasma comprising ammonia and
argon, helium plasma, argon plasma, hydrogen plasma, an in-situ or
remote plasma source based plasma comprising hydrogen and helium,
an in-situ or remote plasma source based plasma comprising hydrogen
and argon, an in-situ or remote plasma source based plasms
comprising ammonia and hydrogen, an in-situ or remote plasma source
based organic amine plasma, an in-situ or remote plasma source
based plasma comprising oxygen, an in-situ or remote plasma source
based plasma comprising oxygen and hydrogen, and mixtures
thereof.
3. The method of claim 1 further comprising the step of subjecting
the coating to a thermal treatment at one or more temperatures
between about 100.degree. C. to about 1000.degree. C. to densify at
least a portion of the coating and form a hardened layer.
4. The method of claim 3 further comprising the step of exposing
the hardened layer to energy selected from the group consisting of
a plasma, infrared light, chemical treatment, an electron beam, or
UV light to form the final silicon-containing film.
5. The method of claim 4 wherein the above steps define one cycle
for the method and the cycle can be repeated until the desired
thickness of the silicon-containing film is obtained.
6. The method of claim 1 wherein the at least one
silicon-containing compound having at least one acetoxy group
comprises diacetoxydimethylsilane.
7. The method of claim 1 wherein R is selected from the group
consisting of methyl, ethyl, n-propyl, iso-propyl, tert-butyl,
n-butyl, sec-butyl, and iso-butyl; and R.sup.1 is selected from the
group consisting of methyl, ethyl, vinyl, allyl, and ethynyl.
8. The method of claim 1 wherein the silicon containing film has a
dielectric constant of <3.0 as determined by Capacitance-Voltage
measurements, a porosity of >10% as measured by Ellipsometric
Porosimetry.
9. A silicon containing film obtained by the method of claim 1
having a dielectric constant of <3.0 as determined by
Capacitance-Voltage measurements, a porosity of >10 volume % as
measured by Ellipsometric Porosimetry upon a substrate having at
least one surface feature.
Description
BACKGROUND
Described herein is a process for the fabrication of an electronic
device. More specifically, described herein are compositions for
forming a silicon-containing film in a deposition process, such as,
for example, a flowable chemical vapor deposition. Exemplary
silicon-containing films that can be deposited using the
compositions and methods described herein include silicon oxide,
silicon nitride, silicon oxynitride or carbon-doped silicon oxide
or carbon-doped silicon nitride films.
Flowable oxide deposition methods typically use alkoxysilane
compounds as precursors for silicon-containing films which are
deposited by controlled hydrolysis and condensation reactions. Such
films can be deposited onto a substrate, for example, by applying a
mixture of water and alkoxysilanes, optionally with solvent and/or
other additives such as surfactants and porogens, onto a substrate.
Typical methods for the application of these mixtures include spin
coating, dip coating, spray coating, screen printing,
co-condensation, and ink jet printing. After application to the
substrate and upon application of one or more energy sources such
as, for example, thermal, plasma, and/or other sources, the water
within the mixture can react with the alkoxysilanes to hydrolyze
the alkoxide and/or aryloxide groups and generate silanol species,
which further condense with other hydrolyzed molecules and form an
oligomeric or network structure.
Besides physical deposition or application of the precursor to the
substrate, vapor deposition processes using water and a silicon
containing vapor source for flowable dielectric deposition (FCVD)
have been described, for instance, in U.S. Pat. Nos. 7,541,297;
8,449,942; 8,629,067; 8,741,788; 8,481,403; 8,580,697; 8,685,867;
7,498,273; 7,074,690; 7,582,555; 7,888,233, and 7,915,131, as well
as U.S. Publ. No. 2013/0230987 A1, the disclosures of which are
incorporated herein by reference. Typical methods generally relate
to filling gaps on substrates with a solid dielectric material by
forming a flowable liquid film in the gap. The flowable film is
formed by reacting a dielectric precursor which may have a Si--C
bond with an oxidant to form the dielectric material. In certain
embodiments, the dielectric precursor condenses and subsequently
reacts with the oxidant to form dielectric material. In certain
embodiments, vapor phase reactants react to form a condensed
flowable film. Since the Si--C bond is relatively inert towards
reaction with water, the resultant network may be beneficially
functionalized with organic functional groups which impart desired
chemical and physical properties to the resultant film. For
example, the addition of carbon to the network may lower the
dielectric constant of the resultant film.
Another approach to depositing a silicon oxide film using flowable
chemical vapor deposition process is gas phase polymerization. For
example, the prior art has focused on using compounds such as
trisilylamine (TSA) to deposit Si, H, N containing oligomers that
are subsequently oxidized to SiOx films using ozone exposure.
Examples of such approaches include: U.S. Publ. No. 2014/0073144;
U. S. Publ. No. 2013/230987; U.S. Pat. Nos. 7,521,378, 7,557,420,
and 8,575,040; and 7,825,040, the disclosures of which are
incorporated herein by reference.
Regarding the processes that employ trisilylamine (TSA), TSA is
typically delivered into the reaction chamber as a gas, mixed with
ammonia, and activated in a remote plasma reactor to generate
NH.sub.2, NH, H and or N radicals or ions. The TSA reacts with the
plasma activated ammonia and begins to oligomerize to form higher
molecular weight TSA dimers and trimers or other species which
contain Si, N and H. The substrate is placed in the reactor and
cooled to one or more temperatures ranging from about 0 to about
50.degree. C. at a certain chamber pressures and TSA/activated
ammonia mixtures the oligomers begin to condense on the wafers
surface in such a way that they can "flow" to fill the trench
surface feature. In this way, a material which contains Si, N and H
is deposited onto the wafer and fills the trench. In certain
embodiments, a pre-anneal step is performed to allow the film to be
more SiN-like. It is desirable to have a SiN material because the
next process step is oxidation at one or more temperatures ranging
from 100-700.degree. C. using ozone or water. Because of the SiN
bond distance and angles, it is known that as SiN is oxidized to
SiO.sub.2 there is a unit cell volume increase which prevents the
film from shrinking.
Despite the recent activity in the art related to flowable chemical
vapor deposition and other film deposition processes, problems
still remain. One of these problems is related to film composition.
For example, flowable oxide films deposited from the precursor
trisilylamine (TSA) in a gas phase polymerization process yield
films with a high density of Si--H bonds and have a wet etch rates
in dilute HF solutions that are 2.2 to 2.5 times faster than high
quality thermal oxide. Such films are not suitable for low-k film
applications.
In many circumstances, a hardening process, including thermal
annealing, UV cure, or ion/radical densification, may be applied to
the flowable films. The hardening process may remove carbon groups,
hydroxyl groups and smaller molecular weight species from the
deposited materials. Referring now to FIG. 1, this often leaves
voids, cracks or spaces in the hardened material. Such films are
also not suitable for low-k film applications.
Thus, there is a need to provide alternative precursor compounds to
produce silicon-containing films via flow CVD techniques that have
the mechanical integrity and porosity to successfully function as
low-k silicon oxide containing film material.
SUMMARY
The compositions or formulations described herein and methods using
same overcome the problems of the prior art by depositing a
silicon-containing film on at least a portion of the substrate
surface that provides desirable film properties upon
post-deposition treatment. The instant invention can provide a
silicon containing film having: i) a mechanical integrity in terms
of Young's Modulus from about 2 to about 15 GPa, about 4 to about
12 and in some cases about 6 to about 10, ii) a porosity of about
10 to about 30 volume %, about 12 to about 25 and in some cases
about 16 to about 22 (e.g., as measured by eliposmetric
porosimetry), and iii) a dielectric constant of about 2.2 to about
3.0, about 2.4 to about 2.8 and in some cases about 2.5 to about
2.7.
In one aspect, the invention described herein provides a method for
depositing a silicon-containing film, the method comprising:
placing a substrate comprising at least one surface feature into a
reactor which is at a temperature of from about -20.degree. C. to
about 400.degree. C.; introducing into the reactor at least one
silicon-containing compound having at least one acetoxy group,
wherein the at least one silicon-containing compound is selected
from the group consisting of:
I(a). Acyloxysilanes with a formula of
(RCOO).sub.mR.sup.1.sub.nSiH.sub.p wherein R is selected from
hydrogen, a linear or branched C.sub.1 to C.sub.6 alkyl group;
R.sup.1 is selected from a linear or branched C.sub.1 to C.sub.6
alkyl group, a linear or branched C.sub.2 to C.sub.6 alkenyl group,
a linear or branched C.sub.2 to C.sub.6 alkynyl group; m=2 or 3;
n=1 or 2; p=0 or 1; and m+n+p=4;
I(b). Acyloxyalkoxysilanes with a formula of
(RCOO).sub.m(R.sup.2O).sub.nSiH.sub.pR.sup.1.sub.q wherein R is
selected from hydrogen, a linear or branched C.sub.1 to C.sub.6
alkyl group; R.sup.1 is selected from a linear or branched C.sub.1
to C.sub.6 alkyl group, a linear or branched C.sub.2 to C.sub.6
alkenyl group, a linear or branched C.sub.2 to C.sub.6 alkynyl
group; R.sup.2 is selected from a linear or branched C.sub.1 to
C.sub.6 alkyl group; m=2 or 3; m=1 or 2; p=0 or 1; q=0 or 1 and
m+n+p+q=4; and
I(c). Acyloxyaminoxysilanes with a formula of
(RCOO).sub.m(R.sup.3R.sup.4NO).sup.nSiH.sub.pR.sup.1.sub.q wherein
R is selected from hydrogen, a linear or branched C.sub.1 to
C.sub.6 alkyl group; R.sup.1 is selected from a linear or branched
C.sub.1 to C.sub.6 alkyl group, a linear or branched C.sub.2 to
C.sub.6 alkenyl group, a linear or branched C.sub.2 to C.sub.6
alkynyl group; and R.sup.3 is selected from hydrogen, a linear or
branched C.sub.1 to C.sub.10 alkyl group; R.sup.4 is selected from
a linear or branched C.sub.1 to C.sub.6 alkyl group; m=2 or 3; n=1
or 2; p=0 or 1; q=0 or 1 and m+n+p+q=4; and providing a plasma into
the reactor to at least partially react the at least one
silicon-containing compound to form a flowable liquid oligomer
wherein the flowable liquid oligomer forms a coating on the
substrate and at least partially fills at least a portion of the at
least one surface feature.
In another aspect, the method of the present invention further
comprises the step of subjecting the coating to a thermal treatment
at one or more temperatures between about 100.degree. C. to about
1000.degree. C. to densify at least a portion of the coating and
form a hardened layer.
In still another aspect, the method of the present invention
further comprises the step of exposing the hardened layer to energy
selected from the group consisting of a plasma, infrared light,
chemical treatment, an electron beam, or UV light to form the final
silicon-containing film.
Another aspect of the invention relates to a precursor composition
comprising at least one silicon-containing compound having at least
one acetoxy group, wherein the at least one silicon-containing
compound is selected from the group consisting of: I(a).
Acyloxysilanes with a formula of (RCOO).sub.mR.sup.1.sub.nSiH.sub.p
wherein R is selected from hydrogen, a linear or branched C.sub.1
to C.sub.6 alkyl group; R.sup.1 is selected from a linear or
branched C.sub.1 to C.sub.6 alkyl group, a linear or branched
C.sub.2 to C.sub.6 alkenyl group, a linear or branched C.sub.2 to
C.sub.6 alkynyl group; m=2 or 3; n=1 or 2; p=0 or 1; and
m+n+p=4;
I(b). Acyloxyalkoxysilanes with a formula of
(RCOO).sub.m(R.sup.2O).sub.nSiH.sub.pR.sup.1.sub.q wherein R is
selected from hydrogen, a linear or branched C.sub.1 to C.sub.6
alkyl group; R.sup.1 is selected from a linear or branched C.sub.1
to C.sub.6 alkyl group, a linear or branched C.sub.2 to C.sub.6
alkenyl group, a linear or branched C.sub.2 to C.sub.6 alkynyl
group; R.sup.2 is selected from a linear or branched C.sub.1 to
C.sub.6 alkyl group; m=2 or 3; m=1 or 2; p=0 or 1; q=0 or 1 and
m+n+p+q=4; and
I(c). Acyloxyaminoxysilanes with a formula of
(RCOO).sub.m(R.sup.3R.sup.4NO).sub.nSiH.sub.pR.sup.1.sub.q wherein
R is selected from hydrogen, a linear or branched C.sub.1 to
C.sub.6 alkyl group; R.sup.1 is selected from a linear or branched
C.sub.1 to C.sub.6 alkyl group, a linear or branched C.sub.2 to
C.sub.6 alkenyl group, a linear or branched C.sub.2 to C.sub.6
alkynyl group; and R.sup.3 is selected from hydrogen, a linear or
branched C.sub.1 to C.sub.10 alkyl group; R.sup.4 is selected from
a linear or branched C.sub.1 to C.sub.6 alkyl group; m=2 or 3; n=1
or 2; p=0 or 1; q=0 or 1 and m+n+p+q=4.
Another aspect of the invention relates to a film obtained by the
inventive method and composition.
Other features and advantages of the present invention will be
apparent from the following more detailed description of the
preferred embodiment, taken in conjunction with the accompanying
drawings which illustrate, by way of example, the principles of the
invention.
The embodiments and features of the present invention can be used
alone or in combinations with each other.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will hereinafter be described in conjunction
with the appended figures wherein like numerals denote like
elements:
FIG. 1 is a SEM micrograph showing a silicon oxide film of the
prior art formed in trenches of a substrate wherein voids formed
during the hardening process;
FIG. 2 is a SEM micrograph showing a silicon oxide film formed
according to the process of the present invention via deposition of
diacetoxydimethylsilane with 02;
FIG. 3 is a SEM micrograph showing the silicon oxide film of FIG. 2
after thermal annealing at 300.degree. C. for 5 min according to
the process of the present invention; and
FIG. 4 is a SEM micrograph showing the silicon oxide film of FIG. 3
after UV exposure for 10 min at 400.degree. C. according to the
process of the present invention.
DETAILED DESCRIPTION
The ensuing detailed description provides preferred exemplary
embodiments only, and is not intended to limit the scope,
applicability, or configuration of the invention. Rather, the
ensuing detailed description of the preferred exemplary embodiments
will provide those skilled in the art with an enabling description
for implementing the preferred exemplary embodiments of the
invention. Various changes may be made in the function and
arrangement of elements without departing from the spirit and scope
of the invention, as set forth in the appended claims.
In the claims, letters may be used to identify claimed method steps
(e.g. a, b, and c). These letters are used to aid in referring to
the method steps and are not intended to indicate the order in
which claimed steps are performed, unless and only to the extent
that such order is specifically recited in the claims.
The compositions or formulations described herein and methods using
same overcome the problems of the prior art by depositing a
silicon-containing film on at least a portion of the substrate
surface that provides desirable film properties upon
post-deposition treatment.
The present invention is directed to semiconductor thin film
process techniques. Methods and system are described for improving
quality of the dielectric film morphologically adapted over various
device structures. More particularly, embodiments of the invention
provide methods and systems of forming silicon oxide film with
increased density to achieve void free gap fill for trenches having
a high aspect ratio. For example, the invention is applied to form
high quality silicon oxide films for filling narrow STI trenches,
among other applications.
Accordingly, in one aspect, the present development provides a
method for depositing a silicon-containing film, the method
comprising: placing a substrate comprising at least one surface
feature into a reactor which is at a temperature of from about
-20.degree. C. to about 400.degree. C.; introducing into the
reactor at least one silicon-containing compound having at least
one acetoxy group, wherein the at least one silicon-containing
compound is selected from the group consisting of:
I(a). Acyloxysilanes with a formula of
(RCOO).sub.mR.sup.1.sub.nSiH.sub.p wherein R is selected from
hydrogen, a linear or branched C.sub.1 to C.sub.6 alkyl group;
R.sup.1 is selected from a linear or branched C.sub.1 to C.sub.6
alkyl group, a linear or branched C.sub.2 to C.sub.6 alkenyl group,
a linear or branched C.sub.2 to C.sub.6 alkynyl group; m=2 or 3;
n=1 or 2; p=0 or 1; and m+n+p=4;
I(b). Acyloxyalkoxysilanes with a formula of
(RCOO).sub.m(R.sup.2O).sub.nSiH.sub.pR.sup.1.sub.q wherein R is
selected from hydrogen, a linear or branched C.sub.1 to C.sub.6
alkyl group; R.sup.1 is selected from a linear or branched C.sub.1
to C.sub.6 alkyl group, a linear or branched C.sub.2 to C.sub.6
alkenyl group, a linear or branched C.sub.2 to C.sub.6 alkynyl
group; R.sup.2 is selected from a linear or branched C.sub.1 to
C.sub.6 alkyl group; m=2 or 3; m=1 or 2; p=0 or 1; q=0 or 1 and
m+n+p+q=4; and
I(c). Acyloxyaminoxysilanes with a formula of
(RCOO).sub.m(R.sup.3R.sup.4NO).sub.nSiH.sub.pR.sup.1.sub.q wherein
R is selected from hydrogen, a linear or branched C.sub.1 to
C.sub.6 alkyl group; R.sup.1 is selected from a linear or branched
C.sub.1 to C.sub.6 alkyl group, a linear or branched C.sub.2 to
C.sub.6 alkenyl group, a linear or branched C.sub.2 to C.sub.6
alkynyl group; and R.sup.3 is selected from hydrogen, a linear or
branched C.sub.1 to C.sub.10 alkyl group; R.sup.4 is selected from
a linear or branched C.sub.1 to C.sub.6 alkyl group; m=2 or 3; n=1
or 2; p=0 or 1; q=0 or 1 and m+n+p+q=4; and providing a plasma into
the reactor to at least partially react the at least one
silicon-containing compound to form a flowable liquid oligomer
wherein the flowable liquid oligomer forms a coating on the
substrate and at least partially fills at least a portion of the at
least one surface feature.
By "flowable liquid oligomer" it is meant a polysiloxane material
that is flowable under deposition conditions wherein the
polysiloxane is measured via FTIR. After curing the flowable liquid
oligomer forms a solid carbon doped porous OSG
The silicon-containing film is selected from the group consisting
of a silicon nitride, a silicon carbide, a silicon oxide, a
carbon-doped silicon nitride, a silicon oxynitride, and a
carbon-doped silicon oxynitride film. The compositions can be
pre-mixed compositions, pre-mixtures (mixed before being used in
the deposition process), or in-situ mixtures (mixed during the
deposition process). Thus, in this disclosure the terms "mixture",
"formulation", and "composition" are interchangeable.
Throughout the description, the term "silicon oxide" as used herein
refers to a film comprising silicon and oxygen selected from the
group consisting of stoichiometric or non-stoichiometric silicon
oxide, carbon doped silicon oxide, silicon carboxynitride and there
mixture thereof.
In the method of the present development, typically the first step
is placing a substrate comprising at least one surface feature into
a reactor which is at a temperature of from about -20.degree. C. to
about 400.degree. C. Suitable substrates include, but are not
limited to, semiconductor materials such as gallium arsenide
("GaAs"), boronitride ("BN") silicon, and compositions containing
silicon such as crystalline silicon, polysilicon, amorphous
silicon, epitaxial silicon, silicon dioxide ("SiO.sub.2"), silicon
carbide ("SiC"), silicon oxycarbide ("SiOC"), silicon nitride
("SiN"), silicon carbonitride ("SiCN"), organosilicate glasses
("OSG"), organofluorosilicate glasses ("OFSG"), fluorosilicate
glasses ("FSG"), and other appropriate substrates or mixtures
thereof. Substrates may further comprise a variety of layers to
which the film is applied thereto such as, for example,
antireflective coatings, photoresists, organic polymers, porous
organic and inorganic materials, metals such as copper and
aluminum, or diffusion barrier layers, e.g., TiN, Ti(C)N, TaN,
Ta(C)N, Ta, W, WN, TiSiN, TaSiN, SiCN, TiSiCN, TaSiCN, or W(C)N.
The organosilicate glass films of the present invention are
preferably capable of adhering to at least one of the foregoing
materials sufficiently to pass a conventional pull test, such as an
ASTM D3359-95a tape pull test.
In some embodiments, the substrate may be a single crystal silicon
wafer, a wafer of silicon carbide, a wafer of aluminum oxide
(sapphire), a sheet of glass, a metallic foil, an organic polymer
film or may be a polymeric, glass, silicon or metallic
3-dimensional article. The substrate may be coated with a variety
of materials well known in the art including films of silicon
oxide, silicon nitride, amorphous carbon, silicon oxycarbide,
silicon oxynitride, silicon carbide, gallium arsenide, gallium
nitride and the like. These coatings may completely coat the
substrate, may be in multiple layers of various materials and may
be partially etched to expose underlying layers of material. The
surface may also have on it a photoresist material that has been
exposed with a pattern and developed to partially coat the
substrate.
In some embodiments, the substrate comprises a surface feature. The
term "surface feature," as used herein, means that the substrate or
partially fabricated substrate that comprises one or more of the
following pores, trenches, shallow trench isolation (STI), vias,
reentrant feature, or the like. In one particular embodiment, the
surface feature(s) have a width of 100 .mu.m or less, 1 .mu.m in
width or less, or 0.5 .mu.m in width or less, or 50 nm in width or
less. In this or other embodiments, the aspect ratio (the depth to
width ratio) of the surface features, if present, is 0.1:1 or
greater, or 1:1 or greater, or 10:1 or greater, or 20:1 or greater,
or 40:1 or greater.
The method used to form the films or coatings described herein are
flowable chemical deposition processes. Examples of suitable
deposition processes for the method disclosed herein include, but
are not limited to, thermal chemical vapor deposition (CVD) or
plasma enhanced cyclic CVD (PECCVD) process. An exemplary flowable
CVD reactor is disclosed in U.S. Publ. No. 2014/0073144; hereby
incorporated by reference. As used herein, the term "flowable
chemical vapor deposition processes" refers to any process wherein
a substrate is exposed to one or more volatile precursors, which
react and/or decompose on the substrate surface to provide flowable
oligomeric silicon-containing species and then produce the solid
film or material upon further treatment. Although the precursors,
reagents and sources used herein may be sometimes described as
"gaseous", it is understood that the precursors can be either
liquid or solid which are transported with or without an inert gas
into the reactor via direct vaporization, bubbling or sublimation.
In some case, the vaporized precursors can pass through a plasma
generator. In one embodiment, the films are deposited using a
plasma-based (e.g., remote generated or in situ) CVD process. The
term "reactor" as used herein, includes without limitation, a
reaction chamber or deposition chamber.
In certain embodiments, the substrate may be exposed to one or more
pre-deposition treatments such as, but not limited to, a plasma
treatment, thermal treatment, chemical treatment, ultraviolet light
exposure, electron beam exposure, and combinations thereof to
affect one or more properties of the films. These pre-deposition
treatments may occur under an atmosphere selected from inert,
oxidizing, and/or reducing.
Although the chemical reagents used herein may be sometimes
described as "gaseous," it is understood that the chemical reagents
may be delivered directly as a gas to the reactor, delivered as
vapors from vaporizing liquid or bubbling liquid using carrier gas
such as nitrogen, helium or argon, vapors from subliming solid
and/or transported by an inert carrier gas into the reactor.
The method of the present development includes the step of
introducing into the reactor a silicon-containing compound (also
referred to herein as a "precursor") having at least one acetoxy
group wherein the at least one second compound is selected from the
group consisting of the following Formula I(a) to I(c):
I(a). Acetoxysilanes with a formula of
(RCOO).sub.mR.sup.1.sub.nSiH.sub.p wherein R and R.sup.1 are
independently selected from a linear or branched C.sub.1 to C.sub.6
alkyl group; m=2 or 3; n=1 or 2; p=0 or 1; and m+n+p=4;
I(b). Acetoxyalkoxysilanes with a formula of
(RCOO).sub.m(R1O).sub.nSiH.sub.p wherein R and R.sup.1 are
independently selected from a linear or branched C.sub.1 to C.sub.6
alkyl group; m=2 or 3; m=1 or 2; p=0 or 1; and m+n+p=4; and
I(c). Acetoxyaminoxysilanes with a formula of
(RCOO).sub.m(R.sup.2R.sup.3NO).sub.nSiH.sub.p wherein R is selected
from a linear or branched C.sub.1 to C.sub.6 alkyl group; R.sup.2
is selected from hydrogen, a branched C.sub.1 to C.sub.10 alkyl
group, and a C.sub.4 to C.sub.10 aryl group; and R.sup.3 is
selected from a linear or branched C.sub.1 to C.sub.10 alkyl group;
m=2 or 3; n=1 or 2; p=0 or 1; and m+n+p=4.
In the formulae above and throughout the description, the term
"linear alkyl" denotes a linear functional group having from 1 to
10, 3 to 10, or 1 to 6 carbon atoms. In the formulae above and
throughout the description, the term "branched alkyl" denotes a
linear functional group having from 3 to 10, or 1 to 6 carbon
atoms. Exemplary linear alkyl groups include, but are not limited
to, methyl, ethyl, propyl, butyl, pentyl, and hexyl groups.
Exemplary branched alkyl groups include, but are not limited to,
isopropyl, isobutyl, sec-butyl, tert-butyl, iso-pentyl,
tert-pentyl, isohexyl, and neohexyl. In certain embodiments, the
alkyl group may have one or more functional groups such as, but not
limited to, an alkoxy group, a dialkylamino group or combinations
thereof, attached thereto. In other embodiments, the alkyl group
does not have one or more functional groups attached thereto. The
alkyl group may be saturated or, alternatively, unsaturated.
In the formulae above and throughout the description, the term
"aryl" denotes an aromatic cyclic functional group having from 3 to
10 carbon atoms, from 5 to 10 carbon atoms, or from 6 to 10 carbon
atoms. Exemplary aryl groups include, but are not limited to,
phenyl, benzyl, chlorobenzyl, tolyl, and o-xylyl.
In the formulae above and throughout the description, the term
"alkenyl group" denotes a group which has one or more carbon-carbon
double bonds and has from 2 to 12, from 2 to 10, or from 2 to 6
carbon atoms. Exemplary alkenyl groups include, but are not limited
to, vinyl or allyl groups.
The term "alkynyl group" denotes a group which has one or more
carbon-carbon triple bonds and has from 2 to 10 or from 2 to 6
carbon atoms. Exemplary alkenyl groups include, but are not limited
to, ethynyl.
In certain embodiments, one or more of the alkyl group or aryl
groups in the formulae may be "substituted" or have one or more
atoms or group of atoms substituted in place of, for example, a
hydrogen atom. Exemplary substituents include, but are not limited
to, oxygen, sulfur, halogen atoms (e.g., F, Cl, I, or Br),
nitrogen, alkyl groups, and phosphorous. In other embodiments, one
or more of the alkyl group, alkenyl group, alkynyl group, aromatic
and/or aryl group in the formulae may be unsubstituted.
In certain embodiments, any one or more of substituents R.sup.1,
R.sup.2, and R.sup.3 in the formulae described above can be linked
with a C--C bond in the above formula to form a ring structure when
they are not hydrogen. As the skilled person will understand, the
substituent may be selected from a linear or branched C.sub.1 to
C.sub.10 alkylene moiety; a C.sub.2 to C.sub.12 alkenylene moiety;
a C.sub.2 to C.sub.12 alkynylene moiety; a C.sub.4 to C.sub.10
cyclic alkyl moiety; and a C.sub.6 to C.sub.10 arylene moiety. In
these embodiments, the ring structure can be unsaturated such as,
for example, a cyclic alkyl ring, or saturated, for example, an
aryl ring. Further, in these embodiments, the ring structure can
also be substituted or substituted. In other embodiments, any one
or more of substituents R.sup.1, R.sup.2 and R.sup.3 are not
linked.
In embodiments wherein the silicon-containing precursor comprises a
compound having Formula I(a), examples of precursors include the
following:
##STR00001##
Examples of compounds of Formula I(a) include
diacetoxydimethylsilane, diacetoxymethylsilane,
triacetoxymethylsilane, diacetoxydivinylsilane,
diacetoxymethylvinylsilane, triacetoxyvinylsilane,
diacetoxydiethynylsilane, diacetoxymehylethynylsilane, and
triacetoxyethynylsilane.
In embodiments wherein the silicon-containing precursor comprises a
compound having Formula I(b), examples of precursors include the
following:
##STR00002##
Examples of compounds of Formula I(B) include
diacetoxymethoxymethylsilane, diacetoxydimethoxysilane, and
triacetoxymethoxysilane.
In embodiments wherein the silicon-containing precursor comprises a
compound having Formula I(c):
##STR00003##
Examples of compounds of Formula I(c) include
diacetoxydimethylaminoxymethylsilane,
diacetoxydi(methylethyl)aminoxymethylsilane, and
diacetoxydiethylaminoxymethylsilane.
The silicon-containing precursor compounds described herein may be
delivered to the reaction chamber such as a CVD or ALD reactor in a
variety of ways. In one embodiment, a liquid delivery system may be
utilized. In an alternative embodiment, a combined liquid delivery
and flash vaporization process unit may be employed, such as, for
example, the turbo vaporizer manufactured by MSP Corporation of
Shoreview, Minn., to enable low volatility materials to be
volumetrically delivered, which leads to reproducible transport and
deposition without thermal decomposition of the precursor. In
liquid delivery formulations, the precursors described herein may
be delivered in neat liquid form, or alternatively, may be employed
in solvent formulations or compositions comprising same. Thus, in
certain embodiments the precursor formulations may include solvent
component(s) of suitable character as may be desirable and
advantageous in a given end use application to form a film on a
substrate.
The silicon-containing precursor compounds are preferably
substantially free of halide ions such as chloride or metal ions
such as Al. As used herein, the term "substantially free" as it
relates to halide ions (or halides) or metal ions such as, for
example, chlorides, fluorides, bromides, iodides, Al.sup.3+ ions,
Fe.sup.2+, Fe.sup.3+, Ni.sup.2+, Cr.sup.3+ means less than 5 ppm
(by weight), preferably less than 3 ppm, and more preferably less
than 1 ppm, and most preferably 0 ppm of each halide or metal ions.
Chlorides or metal ions are known to act as decomposition catalysts
for silicon precursors. Significant levels of chloride in the final
product can cause the silicon precursors to degrade. The gradual
degradation of the silicon precursors may directly impact the film
deposition process making it difficult for the semiconductor
manufacturer to meet film specifications. In addition, the
shelf-life or stability is negatively impacted by the higher
degradation rate of the silicon precursors thereby making it
difficult to guarantee a 1-2 year shelf-life. Moreover, silicon
precursors are known to form flammable and/or pyrophoric gases upon
decomposition such as hydrogen and silane. Compositions comprising
the instant precursor compounds are substantially free of such
decomposition products. Therefore, the accelerated decomposition of
the silicon-containing precursors presents safety and performance
concerns related to the formation of these flammable and/or
pyrophoric gaseous byproducts.
Silicon-containing precursors according to the present invention
that are substantially free of halides can be achieved by (1)
reducing or eliminating chloride sources during chemical synthesis,
and/or (2) implementing an effective purification process to remove
chloride from the crude product such that the final purified
product is substantially free of chlorides. Chloride sources may be
reduced during synthesis by using reagents that do not contain
halides such as chlorodislanes, bromodisilanes, or iododislanes
thereby avoiding the production of by-products that contain halide
ions. In addition, the aforementioned reagents should be
substantially free of chloride impurities such that the resulting
crude product is substantially free of chloride impurities. In a
similar manner, the synthesis should not use halide based solvents,
catalysts, or solvents which contain unacceptably high levels of
halide contamination. The crude product may also be treated by
various purification methods to render the final product
substantially free of halides such as chlorides. Such methods are
well described in the prior art and, may include, but are not
limited to purification processes such as distillation, or
adsorption. Distillation is commonly used to separate impurities
from the desire product by exploiting differences in boiling point.
Adsorption may also be used to take advantage of the differential
adsorptive properties of the components to effect separation such
that the final product is substantially free of halide. Adsorbents
such as, for example, commercially available MgO--Al.sub.2O.sub.3
blends can be used to remove halides such as chloride.
For those embodiments relating to a composition comprising a
solvent(s) and at least one silicon-containing compound described
herein, the solvent or mixture thereof selected does not react with
the silicon compound. The amount of solvent by weight percentage in
the composition ranges from 0.5% by weight to 99.5% or from 10% by
weight to 75%. In this or other embodiments, the solvent has a
boiling point (b.p.) similar to the b.p. of the precursors of
Formulae I(a), I(b), and I(c) or the difference between the b.p. of
the solvent and the b.p. of the silicon precursor precursors of
Formulae I(a), I(b), and I(c) is 40.degree. C. or less, 30.degree.
C. or less, or 20.degree. C. or less, 10.degree. C. or less, or
5.degree. C. or less. Alternatively, the difference between the
boiling points ranges from any one or more of the following
end-points: 0, 10, 20, 30, or 40.degree. C. Examples of suitable
ranges of b.p. difference include without limitation, 0.degree. C.
to 40.degree. C., 20.degree. C. to 30.degree. C., or 10.degree. C.
to 30.degree. C. Examples of suitable solvents in the compositions
include, but are not limited to, an ether (such as 1,4-dioxane,
dibutyl ether), a tertiary amine (such as pyridine,
1-methylpiperidine, 1-ethylpiperidine, N,N'-Dimethylpiperazine,
N,N,N',N'-Tetramethylethylenediamine), a nitrile (such as
benzonitrile), an alkyl hydrocarbon (such as octane, nonane,
dodecane, ethylcyclohexane), an aromatic hydrocarbon (such as
toluene, mesitylene), a tertiary aminoether (such as
bis(2-dimethylaminoethyl) ether), or mixtures thereof.
In one particular embodiment, the introducing step, wherein the at
least one silicon-containing compound is introduced into the
reactor, is conducted at one or more temperatures ranging from
-20.degree. C. to 1000.degree. C., or from about 400.degree. C. to
about 1000.degree. C., or from about 400.degree. C. to about
600.degree. C., or from about -20.degree. C. to about 400.degree.
C. In these or other embodiments, the substrate comprises a
semiconductor substrate comprising a surface feature.
The method of the present invention includes the step of providing
an in-situ plasma or remote plasma source to at least partially
react the at least one silicon-containing compound to form a
flowable liquid oligomer wherein the flowable liquid oligomer forms
a coating on the substrate and at least partially fills at least a
portion of the at least one surface feature. Energy is applied to
the at least one silicon-containing compound, nitrogen-containing
source (if employed), oxygen source, other precursors or
combination thereof to induce reaction and to form the
silicon-containing film or coating on the substrate. Such energy
can be provided by, but not limited to, thermal, plasma, pulsed
plasma, helicon plasma, high density plasma, inductively coupled
plasma, X-ray, e-beam, photon, remote plasma methods, and
combinations thereof. In certain embodiments, a secondary RF
frequency source can be used to modify the plasma characteristics
at the substrate surface. In embodiments wherein the deposition
involves plasma, the plasma-generated process may comprise a direct
plasma-generated process in which plasma is directly generated in
the reactor, or alternatively a remote plasma-generated process in
which plasma is generated outside of the reactor and supplied into
the reactor.
The volume flow ratio of precursor to oxygen or nitrogen containing
source can range from about 40:1 to about 0.2:1, about 20:1 to
about 1:1 and in some cases about 6:1 to about 2:1. In one
embodiment of the invention, a composition comprises the inventive
silicon containing precursor and at least one of the oxygen or
nitrogen containing source. In another embodiment of the invention,
a composition comprises an oligomer obtained from the inventive
precursor and at least one of oxygen or nitrogen containing
source.
In one particular embodiment, the plasma is selected from but not
limited to the group consisting of a nitrogen plasma; plasma
comprising nitrogen and helium; a plasma comprising nitrogen and
argon; an ammonia plasma; a plasma comprising ammonia and helium; a
plasma comprising ammonia and argon; helium plasma; argon plasma;
hydrogen plasma; a plasma comprising hydrogen and helium; a plasma
comprising hydrogen and argon; a plasma comprising ammonia and
hydrogen; an organic amine plasma; a plasma comprising oxygen; a
plasma comprising oxygen and hydrogen, and mixtures thereof.
In another embodiment, the plasma source is selected from but not
limited to the group consisting of a carbon source plasma,
including a hydrocarbon plasma, a plasma comprising hydrocarbon and
helium, a plasma comprising hydrocarbon and argon, carbon dioxide
plasma, carbon monoxide plasma, a plasma comprising hydrocarbon and
hydrogen, a plasma comprising hydrocarbon and a nitrogen source, a
plasma comprising hydrocarbon and an oxygen source, and mixture
thereof.
As previously mentioned, the method deposits a film upon at least a
portion of the surface of a substrate comprising a surface feature.
The substrate is placed into the reactor and the substrate is
maintained at one or more temperatures ranging from about
-20.degree. C. to about 400.degree. C. In one particular
embodiment, the temperature of the substrate is less than the walls
of the chamber. The substrate temperature is held at a temperature
below 100.degree. C., preferably at a temperature below 25.degree.
C. and most preferably below 10.degree. C. and greater than
-20.degree. C.
In certain embodiments, the reactor is at a pressure below
atmospheric pressure or 750 torr (10.sup.5 Pascals (Pa)) or less,
or 100 torr (13332 Pa) or less. In other embodiments, the pressure
of the reactor is maintained at a range of about 0.1 torr (13 Pa)
to about 10 torr (1333 Pa).
In the presence of the plasma energy, the silicon-containing
compounds react with each other and form oligomers which condense
as a liquid (liquid oligomers) on the surface of the substrate and
at least partially fill the features on the substrate. However,
direct use of the as-deposited film can result in a dielectric that
is too porous and does not have an adequate mechanical strength.
Thus, certain embodiments of the present development are applied to
perform further treatment of the as-deposited silicon oxide layer
to improve film quality with increased density and still achieve a
void free gap fill. By "void free" it is meant a visual
determination obtained by viewing an SEM or TEM of the deposited
and cured film.
In preferred embodiments, the flowable liquid oligomer is thermally
annealed at one or more temperatures ranging from about 100.degree.
C. to about 1000.degree. C. to densify at least a portion of the
materials followed by broadband UV treatment at the temperature
ranging from 100.degree. C. to 1000.degree. C.
To prevent voiding formation, cross-linking is needed during the
treatment. For example, when diacetoxydimethylsilane is heated, an
acetic anhydride molecule is lost and Si--O--Si bonds are formed.
The loss of an acetic anhydride molecule leads to the creation and
nanoscale pores. Since there are two acetoxy groups on each silicon
atom, the cross-linking formation leads to long chains. To create
3-D cross-linking, a precursor with three acetoxy functional groups
is needed. In other embodiments, an oxidant (O.sub.2 or CO.sub.2)
is preferably added to create 3-D cross-linking. Film densities
typically range from 1.5 to 2.0 g/cm.sup.3 for silicon oxide or
carbon doped silicon oxide and 1.8 to 2.8 g/cm.sup.3 for silicon
nitride or carbon doped silicon nitride. Thus, such films are
suitable for use as low-k material applications. The dielectric
constant, k, achieved typically ranges from 2.5 to 2.8, or 2.5 to
3.0, for carbon doped silicon oxide.
In certain embodiments, the resultant silicon-containing films or
coatings can be exposed to a post-deposition treatment such as, but
not limited to, a plasma treatment including, but not limited to,
hydrogen plasma, helium plasm, argon plasma, ammonia plasma, water
(H.sub.2O) plasma, oxygen plasma, ozone (O.sub.3) plasma, NO
plasma, N.sub.2O plasma, carbon monoxide (CO) plasma, carbon
dioxide (CO.sub.2) plasma and combinations thereof, chemical
treatment, ultraviolet light exposure, infrared exposure, electron
beam exposure, and/or other treatments to affect one or more
properties of the film.
In some embodiments, the post thermal treatment materials are
exposed to a plasma, infrared lights, chemical treatment, an
electron beam, or UV light to form a dense film.
The above steps define one cycle for the methods described herein;
and the cycle can be repeated until the desired thickness of a
silicon-containing film is obtained. In this or other embodiments,
it is understood that the steps of the methods described herein may
be performed in a variety of orders, may be performed sequentially
or concurrently (e.g., during at least a portion of another step),
and any combination thereof. The respective step of supplying the
compounds and other reagents may be performed by varying the
duration of the time for supplying them to change the
stoichiometric composition of the resulting silicon-containing
film.
In one embodiment of the invention, at least one of the following
films or features can be formed or deposited upon the inventive
silicon containing film: i) subject to planarization, ii) copper
(e.g., to fill vias), and iii) dielectric films. In one aspect, the
instant invention comprises a substrate comprising patterned
structure having at least one feature (e.g., via or trench) upon
which the inventive film (e.g., carbon doped silicon oxide) is
deposited and a film comprising a barrier layer (e.g., at least one
of cobalt, silicon carbonitride, silicon nitride, carbon
oxynitride, TiN and TaN) deposited upon the inventive film.
The following examples are provided for the purpose of further
illustrating the present invention but are by no means intended to
limit the same.
EXAMPLES
Flowable chemical vapor deposition (FCVD) films were deposited onto
medium resistivity (8-12 .OMEGA.cm) single crystal silicon wafer
substrates and Si pattern wafers. In certain examples, the
resultant silicon-containing films or coatings can be exposed to a
pre-deposition treatment such as, but not limited to, a plasma
treatment, thermal treatment, chemical treatment, ultraviolet light
exposure, Infrared exposure, electron beam exposure, and/or other
treatments to affect one or more properties of the film.
Depositions on a modified FCVD chamber on an Applied Materials
Precision 5000 system, can be performed using either a silane or a
TEOS process kit. The chamber has direct liquid injection (DLI)
delivery capability. The precursors are liquids with delivery
temperatures dependent on the precursor's boiling point.
To deposit initial flowable carbon doped oxide films, typical
liquid precursor flow rates were 100-5000 mg/min, oxygen (or
alternatively carbon dioxide) flow rates were 20-40 sccm, in-situ
plasma power density was 0.25-3.5 W/cm.sup.2, pressure was 0.75-12
Torr. To densify the as-deposit flowable films, the films were
thermally annealed and/or UV cured in vacuum using the modified
PECVD chamber at 100.about.1000 C, preferably 300.about.400.degree.
C. Thickness and refractive index (RI) at 632 nm were measured by a
SCI reflectometer or Woollam ellipsometer. Typical film thickness
ranged from 10 to 2000 nm. Bonding properties and hydrogen content
(Si--H, C--H and N--H) of the silicon-based films were measured and
analyzed by a Nicolet transmission Fourier transform infrared
spectroscopy (FTIR) tool. All density measurements were
accomplished using X-ray reflectivity (XRR). X-ray Photoelectron
Spectroscopy (XPS) and Secondary ion mass spectrometry (SIMS)
analysis were performed to determine the elemental composition of
the films. The flowability and gap fill effects on patterned wafers
were observed by a cross-sectional Scanning Electron Microscopy
(SEM) using a Hitachi S-4800 system at a resolution of 2.0 nm. The
porosity of the film was measured by ellipsometric porosimetry.
Flowable CVD depositions were conducted using a design of
experiment (DOE) methodology. The experimental design includes:
precursor flows from 100 to 5000 mg/min, preferably 500 to 2000
mg/min; oxygen (or CO.sub.2) flow from 0 sccm to 1000 sccm,
preferably 0 to 100 sccm; pressure from 0.75 to 12 Torr, preferably
6 to 10 Torr; RF power (13.56 MHz) 50 to 1000 W, preferably
100.about.500 W; Low-frequency (LF) power 0 to 100 W; and
deposition temperature ranged from -20 to 400.degree. C.,
preferably -20.degree. C. to 40.degree. C. The DOE experiments were
used to determine what process parameters produced the optimal film
with good flowability.
Deposition of Low-K Film with Diacetoxydimethylsilane as
Precursor
In this experiment, the process conditions used to deposit flowable
porous low-k films with the most favorable film properties are as
follows: power=200 W, spacing=200 mils, pressure=6.about.10 Torr,
Temperature=30.about.35.degree. C.,
diacetoxydimethylsilane=1500.about.2000 mg/min, He=200 sccm,
O2=40.about.60 sccm. The flowable film was thermally annealed at
300.degree. C. for 5 min, followed by 400.degree. C. UV cure for 10
minutes.
Films with RI of 1.37 and k of 2.6.about.2.7 were obtained on
blanket substrates. The porosity of the film was 19.about.20%. With
the processing pressure at 8 Torr, the modulus of the film was 10.4
GPa; hardness was 1.84 GPa. The modulus and hardness were
consistent with conventional PECVD porous low-k films.
Referring now to FIG. 2, FIG. 2 shows a cross-sectional SEM
indicates that good gap-fill was achieved by the deposition of
diacetoxydimethylsilane with O.sub.2. Referring now to FIG. 3, FIG.
3 shows a cross-sectional SEM of the film of FIG. 2 that was
thermally annealed for 5 min at 300.degree. C. and UV cured for 10
min at 400.degree. C. (FIG. 4). Referring now to FIG. 4, FIG. 4 is
a SEM micrograph showing the silicon oxide film of FIG. 3 after UV
exposure for 10 min at 400.degree. C.
While the principles of the invention have been described above in
connection with preferred embodiments, it is to be clearly
understood that this description is made only by way of example and
not as a limitation of the scope of the invention.
* * * * *